排序方式: 共有13条查询结果,搜索用时 500 毫秒
1.
调角器支架是一种结构不对称、形状复杂而精度要求较高的冲压件.对制件成形过程中的应力、应变特点进行了分析,介绍了冲压工艺中采取的措施及模具结构特点. 相似文献
2.
3.
4.
The purpose of the present work is the experimental investigation on the extinguishment of diesel container fires by a water-mist system with base injection through multiple nozzles placed symmetrically at various positions around the rim of the container. Experimental parameters selected are the orifice diameter of the nozzle, the number of nozzles, position of nozzles (angle of orientation, radial and vertical distance of the nozzle from the edge of the container), and injection pressure. Nozzles used in the present work are pressure-swirl nozzles with Z-type swirl-insert with solid-cone spray. Desirable properties of the system such as the non-clogging operation of the nozzle and uniform mass flux density in the spray are tested for the nozzles. The optimized solution is provided considering water consumption and the physical stability of the fuel surface in the container. Displacement of oxygen is observed as a predominant extinction mechanism due to the effective application of spray in the base region of the fire. The present work provides the parametric study of the extinction establishing the feasibility of the water mist system with a base injection for extinguishing tank fires. This may serve as guidelines for the preliminary design of the system with the extension for larger tank fires. 相似文献
5.
S. I. C. O. Santos L. De Neve J. T. Lumeij M. I. Förschler 《Behavioral ecology and sociobiology》2007,61(9):1499-1506
The assessment of plumage colouration has become a common procedure in many ornithological studies, especially after the discovery
of differences between avian and human visual systems, namely the avian ability to perceive ultraviolet wavelengths. There
are many techniques available for plumage colour assessment. Nevertheless, unidirectional reflectance spectrometry seems actually
to be the method of choice and is used in most studies. The active avian visual communication skills, the physical characteristics
of the plumage surface and the birds’ body shape prompted us to study plumage colouration with different angles of incidence
and observation by bidirectional reflectance spectrometry. In this study, we explore the effect of different angles of incidence
and observation, on a single plane of incidence, on the reflectance spectrometric assessment of five differently coloured
body regions of the blue fronted Amazon parrot (Amazona aestiva). Measurements were made using a AVS-USB2000 spectrometer with a DH-2000 light source and two different reflection probes
(bifurcated fibre optic probe and a specially designed fibre holder). The results of this study illustrate clear angle dependence
of colour parameters in differently coloured non-iridescent plumage regions of the blue fronted Amazon parrot. Our results
may have direct implications on the observed transmitted information of display and its associated predation risk (trade-off)
in birds, but also in other animals. Moreover, the results show that unidirectional reflectance spectrometry alone may be
a rather limited procedure to quantify and compare true colour of a complex surface such as birds’ plumage. Therefore, slight
but behavioural important characteristics of plumage pattern may remain undiscovered with this method. 相似文献
6.
7.
8.
选取了尺寸为400mm×90mm×3mm质地较为均匀的白木作为研究对象,对不同试样放置角度和不同外加辐射强度作用下的火焰高度、火蔓延速率和失重速率等火蔓延参数进行了测量,以研究试样放置角度和辐射强度对可炭化固体表面火蔓延的作用规律。研究发现,试样表面的火蔓延速率随辐射强度的增加而增加。当角度在负角度范围内时,角度的变化对火蔓延速率的影响不大,当角度在正角度范围内时,火蔓延速率随着角度的增加而迅速上升。试样失重速率随着辐射强度以及试样放置角度的增加而增加。火焰高度会随着外加辐射强度的增加而增加,并与试样失重速率的0.4次方呈正比关系。 相似文献
9.
Increasing concerns about the spread of airborne pathogens such as severe acute respiratory syndrome (SARS) and novel swine-origin influenza A (H1N1) have attracted public attention to bioaerosols and protection against them. The airborne pathogens are likely to be expelled from coughing or speaking, so the physical data of the exhaled particles plays a key role in analyzing the pathway of airborne viruses. The objective of this study was to analyze the initial velocity and the angle of the exhaled airflow from coughing and speaking of 17 males and 9 females using Particle Image Velocimetry (PIV) and acrylic indoor chamber. The results showed that the average initial coughing velocity was 15.3 m/s for the males and 10.6 m/s for the females, while the average initial speaking velocity was 4.07 m/s and 2.31 m/s respectively. The angle of the exhaled air from coughing was around 38° for the males and 32° for the females, while that of the exhaled air from speaking was around 49° and 78° respectively. Also, the linear relation between the tested subject’s height and their coughing and speaking velocity was shown in this study. 相似文献
10.
Bend structures are common in process industries. These bends containing three typical angles (90°, obtuse angle and acute angle) are often incorporated into pipes or ducts at different positions. In our experiments, the effect of both the bend angle and bend position on flame acceleration was studied. Flame acceleration in a pipe bend can be divided into three stages. The flame speeds increased before the bend and increased again after decreasing for a short distance in the bend. Flame reversing decreased the flame speeds in the bend and led to additional turbulence, which enhanced flame acceleration after the bend. The flame acceleration in three different pipe bend angles had similar trends. The decreasing amplitude of the flame speed in the bend increased with a decrease in the bend angles. The flame speeds in the bend were ordered such that 52° <90° <145°. However, the maximum flame speeds in the pipe were in the opposite order. Additionally, both the flame speeds in the bends and the maximum flame speeds in the whole pipes increased as the bend’s position away from ignition point increased. 相似文献